As for trying stereo microphone configurations other than ORTF, DIN, NOS and the like with your cardioids, start from consideration of the basic relationship governing angle and spacing between any pair of microphones used for stereo recording- 1) The less angle you use between the microphones, the more spacing you should use between them, and vice-a-versa.
A coincident X/Y microphone arrangement requires a very wide angle between microphones to produce a good sounding stereo recording (but don't over do it), whereas a spaced A-B recording with parallel arranged mics requires significantly more space between the microphones (but don't over do it), regardless of the microphone's pickup pattern.
Using a single pair of cardioids, I'd skip trying a coincident configuration for this. In general, the cardioid pattern just isn't directional enough to work very well in a coincident X/Y arrangement for a good-quality stereo recording of an ensemble in a live space. If you consider the 110 degree angle between microphones specified by ORTF to be somewhat on the wide side (which is specified due to the microphone spacing of just 17cm or a bit under 7"), then consider that if those cardioids were placed in X/Y with no spacing between them, even 180 degrees between microphones isn't really enough. Sure, 90 degree X/Y cards will work, but most listeners will prefer DIN, which also uses the same 90 degree angle between mics except with a spacing of 12", producing a much more appropriate pattern/angle/spacing combination for this type of recording. Coincident cardioids have their place, and could work well if you were also recording your omnis, widely spaced to either side of the X/Y cardioids with the intent of mixing the coincident cards and wide-spaced omnis together, but that's getting well ahead of ourselves and complicating things. Let's keep it at 2 channels for now.
If you want to use a angle of less than 90 degrees between cardioids, space them more than 12" apart, possibly a lot more. And increase that spacing the further your recording position is from the source as you move back into the room..
Which leads to the next basic relationship which helps determine what pattern/angle/spacing relationship to choose- 2) As the recording position is moved further away from the source, compensate by using less angle between the microphones and more spacing between them.
So if ORTF works great from the stage-lip, try the same cardioids in a wider spaced but more narrowly angled configuration if you are recording from further back in the room. The logical extreme to that is A-B spaced cardioids with the mics parallel to each other, as if you were using a pair of omnis. That would be appropriate if you had to record from the back of the room, wanted to maximize pickup of the direct sound as much as possible with regards to room reverb, and still wanted to preserve as much "stereoness" as possible given those constraints.
How much space between narrowly angled microphones? Below is a chart which recommends spacings between cardioids based on whatever angle between microphones a taper ends up with after pointing the mics directly at the PA speakers. It takes the point-at-stacks (PAS) taper technique and suggests an appropriate spacing between mics.
Notice that it gets wide quickly as the angle diminishes. As a rough starting point I'd suggest spacing omnis, or in your case parallel angled cardioids, 3 feet apart. More can work, less can work, but 3' is often about right. Consider 3' A-B as a good starting point, sort of like ORTF/DIN/NOS or there about is a good starting point for near-spaced cardioids. Also consider 3' A-B to be something of an extension of the chart above, out to a Mic angle of 0 degrees and a suggested spacing of 100 cm.